Solar collectors of the aforedescribed type are known and, in considering such devices, mention may be made of the advantages of improving the energy absorption efficiency by the solar energy collector, i.e. by blackening an absorber surface.
In a heat exchanger cell of the aforementioned type, a heat carrier, usually water, picks up the solar energy, which has been transformed into sensible heat, to carry this energy to a load or consuming station.
Thus such solar collectors may be used to contribute hot water to the space-heating or water-supply system of a structure or other water heating system thereof or to contribute energy to any industrial, institutional or personal use.
The water generally is passed through respective passages and the thermal-insulating or loss-blocking chamber or space can be composed of a single cell or a multiplicity of cells.
For example, heat exchangers are known (see GLASS SOLAR COLLECTOR DEVELOPMENT, U.S. DEPARTMENT OF COMMERCE, INTERNATIONAL TECHNICAL INVENTION SERVICE PB-253450, PAGE 64) in which the wall of the heat insulating space and thus the wall of the heat exchanger cell turned toward the solar energy input side are composed of glass. In order to improve the heat transmissibility and the solar energy absorption, this wall may be coated by vapor deposition with metals to vary the transmissivity and emission characteristics.
The absorber layer should, in the ideal case, be completely black.
It is also known (see the German Patent Publication-Offenlegungsschrift DE-OS No. 26 11 108) to form the wall of the heat exchanger cell turned toward the insulation side from glass and to coat this wall, on the side thereof at which the insulation is disposed, with absorption-promoting material.
These techniques have proved to be difficult and expensive to carry out and to give rise to solar energy collectors that are fragile, structurally unreliable and prone to failure.
These disadvantages are due only in part to the sensitivity of the glass structure to mechanical stress and the repeated handling to which the solar collector may be subject during transport and mounting. These difficulties can also be attributed in part to the complex manipulations to which the components of the solar collector must be subjected to during manufacture.
Problems are also encountered in the indicated respects when attempts are made to operate the heat exchanger cell under an elevated pressure or to seal the cell against elevated pressure as may be necessary when the solar-energy collector is utilized in a closed system operating under elevated pressure.